It is not recommended to immediately cook frozen lobster tails - instead, Better Homes and Gardens suggests defrosting them first. Allowing the frozen tails to thaw in the refrigerator overnight (8-10 hours) will ensure that the meat is tender.
Once thawed, place the lobster tails in cold water for 30 minutes to an hour. Change the water every 15 minutes so the temperature remains stable. When the meat is fully defrosted the tail flap can easily be bent to the base of the tail with little effort. Uncooked lobster tails retain a mottled, blue-green coloring until cooked.
In order to cook four 8-ounce tails, bring 6 cups of salted water to a boil. A 3-quart saucepan should provide enough space for all four tails. Let the tails simmer uncovered for 8 to 12 minutes or until the shells turn bright red. The meat inside should be tender to the touch.
Lobster tails are a great alternative to buying whole lobsters. According to the Better Homes and Gardens website, the most popular tails are from Spiny lobsters. This species doesn't have claws, and their tails provide more meat than Maine Lobsters. They are sometimes sold as "rock lobster" tails and are available both fresh and frozen.